At the last installation step, just after submitting database parameters, where the page displays "Les paramètres entrés sont corrects" (sorry, french install...), there are some PHP notices and warnings on the page :

Notice: Undefined variable: step in C:\wamp\www\piwigo\install.php on line 200

Notice: Undefined index: dblayer in C:\wamp\www\piwigo\install.php on line 230